Next step: trustless feeds.

How for instance create a trustless quotefeed for BTC/LTC?

Trustless = decentralized. So, build a feed publisher straight into counterpartyd somehow?

Any price of any asset or any outcome of any bet that is to be published fully automated and trustless inevitably must come from one or more electronically published sources. That's because the information has to be available to everyone and needs to be accessible algorithmically.

A price source can be some stream or even a web page. All peers can look up a price themselves and feed it to the network. A price should only be valid and published if for instance 2/3 of the processing power of the network is in agreement.  (Else, no price should be published and any bets or trades depending on this feed should be unwinded. This however should be a rare event as most of the time all peers will be in agreement since the price source they use is hard-coded and the same for all. Processing power can be measured by some proof of work mechanism.)

Now the problem is reduced to finding trustless publisher. Who can be trusted to publish a truthful price? I think the answer is to pick prices from multiple sources. For instance, the price of LTC can be some weighted average of the price (time-weighted) taken from multiple exchanges. Exchanges may cooperate with Counterparty and publish a time weighted price of LTC on a web page every hour so all peers see the same price.

Similarly the price for Gold or any other asset can be hard-coded to be looked up hourly at several websites such as Yahoo, Kitco, Google Finance, Bloomberg etc. When in agreement sufficiently, it could be accepted as a valid quote and fed to the network. If peers are in agreement (2/3 rule) then the price becomes final and is published.